A nonaqueous electrolyte secondary battery such as a nickel-hydride secondary battery and a lithium-ion secondary battery includes an outer case and a power-generating element housed in the outer case (see, for example Patent Document 1). A known power-generating element is a roll-up unit provided by winding, around an axis, a sheet unit including a positive electrode sheet and a negative electrode sheet placed one on another with a separator interposed between them. The roll-up unit of this type is housed within the outer case together with an electrolytic solution in such a state that the roll-up unit is pressed in a diameter direction into a flat shape. The roll-up unit has an exposed portion having no active material applied thereto formed at an end in the axis direction. The exposed portion is pressed in the diameter direction of the roll-up unit into a sheet shape, and is welded to a collector terminal in that pressed state.
Improvements in battery output have been required in recent years, and especially, a higher battery output has been needed in a secondary battery which stores an electric power to be supplied to a motor for running of a vehicle. A possible method of increasing the battery output is to increase the number of turns of the roll-up unit. This method, however, involves an increase in thickness of the roll-up unit, so that it is difficult to press the exposed portion into a sheet shape.
Another possible method is to place an intermediate terminal inside the roll-up unit and to place a collector terminal outside the roll-up unit. The intermediate terminal has a pair of arm portions resistant-welded to an inner face of the exposed portion and a connecting portion connecting the arm portions. The collector terminal is resistance-welded to an outer face of the exposed portion opposite to the arm portion. The resistance welding is performed by pressing electrodes against the arm portion and the collector terminal opposite to each other through the exposed portion and passing an electric current through the electrodes.